.light-1 {
    position: relative;
    color: #21ebff;
    transition: 0.5s;
    border: 0;
    background: transparent;
}

.light-1:hover {
    background: #21ebff;
    color: #111;
    box-shadow: 0 0 40px #21ebff;
    transition-delay: 0.5s;
}

.light-1::before {
    content: "";
    position: absolute;
    top: -5px;
    left: -5px;
    width: 10px;
    height: 10px;
    border-top: 5px solid #21ebff;
    border-left: 5px solid #21ebff;
    transition: 0.5s;
}

.light-1:hover::before {
    width: 100%;
    height: 100%;
}

.light-1::after {
    content: "";
    position: absolute;
    bottom: -5px;
    right: -5px;
    width: 10px;
    height: 10px;
    border-bottom: 5px solid #21ebff;
    border-right: 5px solid #21ebff;
    transition: 0.5s;
}

.light-1:hover::after {
    width: 100%;
    height: 100%;
}